Radiator-Shroud Structure

ABSTRACT

A shroud  15  attached to an air discharge side of a radiator  13  narrows toward a centrifugal-flow-type rotary fan  11  and forms a cylindrical shape. A surrounding portion  17  is provided so as to surround the rotary fan  11 , and a guide portion  19  extending in the centrifugal direction of the rotary fan  11  is provided at the end of the surrounding portion  17 . The length of the guide portion  19  is about 6% the diameter of the rotary fan  11 . Since this mitigates turbulence of centrifugally flowing air  21  flowing out of the rotary fan  11  and suppress a drop in the amount of air passing through the radiator  13 , the cooling capacity of the radiator  13  can be enhanced.

TECHNICAL FIELD

The present invention relates to a radiator-shroud structure which isprovided between a radiator and a fan of a vehicle so as to guide air,and more particularly, to a radiator-shroud structure capable ofpreventing reverse flow of centrifugal flow produced by means of arotary fan.

BACKGROUND ART

As shown in FIG. 5, in a vehicle such as a cab-over-type vehicle 1, anengine section 5 including a radiator 13 and a rotary fan 11 is disposedunder a cab 3, and air (wind) is taken from the outside via an airintake opening provided in an unillustrated front panel in the directionof arrow B, whereby the cooling capacity of the radiator 13 is enhanced.A shroud 15 is provided between the radiator 13 and the rotary fan 11,and guides air discharged from the radiator 13 to the rotary fan 11.

In order to improve cooling capacity, increasing the amount of airpassing through the radiator 13 is important. For such a purpose, therehas been proposed a shroud having a devised shape (see Patent Document1). Patent Document 1: Japanese Patent Application Laid-Open (kokai) No.2002-38952

As shown in FIGS. 6 and 7, in general, the shroud 15 is attached to theradiator 13, and assumes a shape which surrounds the outer circumferenceof the rotary fan 11. That is, as shown in FIG. 6, the radiator 13typically has a rectangular structure, and therefore, the shroud 15assumes a rectangular shape at a connection portion at which the shroud15 is connected to the radiator 13. Further, since the radiator 13 isdisposed at an inclined orientation so as to efficiently use a space, alower side of the shroud 15 assumes a shape narrowing toward the rotaryfan 11. At a position corresponding to the outer circumference of therotary fan 11, the shroud 15 has a cylindrical surrounding portion 17which surrounds the rotary fan 11. Meanwhile, in the cab-over-typevehicle 1, the rotary fan 11 is connected to the engine section 5,because, in general, the rotary fan 11 rotates as a result oftransmission of rotation of a crankshaft of the engine section 5thereto.

Air having passed through the radiator 13 passes through the shroud 15and the rotary fan 11, and is discharged. In some cases, the clearancebetween the end of the fan and the shroud must be increased from theviewpoint of design of the vehicle. In such a case, if an axial flow fanis employed, an air flow leaks through the clearance between the end ofthe fan and the shroud, and the amount of air passing through theradiator 13 decreases. Such a leak, which causes a reduction in theamount of air, can be prevented through employment of a fan whichproduces a centrifugal flow.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, when a rotary fan 11 which produces a centrifugal flow isprovided, air flows not only in the direction of arrow A but also in thedirections of arrows A′ and A″ in FIG. 7, and there arises a problem inthat air flow turbulence occurs at the end of the surrounding portion 17of the shroud 15.

FIG. 8 shows the results of a simulation performed on turbulence of flowof air flowing through the radiator 13, the shroud 15, and the rotaryfan 11 for the case where the shroud 15 is a conventional one. A portioncolored in black corresponds to a region where a large turbulenceoccurs. As can be seen from FIG. 8, the flow of air flowing out of theblade ends of the rotary fan 11 changes to the direction of arrow A′ orA″, and turbulence occurs.

If air flow turbulence occurs at the end of the surrounding portion 17of the shroud 15, it becomes difficult for the air discharged from theradiator 13 to pass the vicinity of the surrounding portion 17, so thatthe amount of air decreases. This causes a drop in the cooling capacityof the radiator.

FIG. 8 also shows a flow of air which reversely flows from the end ofthe rotary fan 11 toward the radiator 13. This reverse flow also hindersthe flow of air discharged from the radiator 13, and lowers the coolingcapacity of the radiator. However, this problem is not related to thepresent invention, and will not be described here.

The present invention has been accomplished in light of the aboveproblems, and an object of the present invention is to provide aradiator-shroud structure which mitigates turbulence of centrifugallyflowing air 21 discharged from the rotary fan 11 so as to suppress adecrease in the amount of air passing through the radiator 13, tothereby enhance the cooling capacity of the radiator 13.

MEANS FOR SOLVING THE PROBLEMS

The present invention, which solves the above-described problem, is aradiator-shroud structure including a rotary fan which produces acentrifugal flow of air, a radiator provided in the vicinity of therotary fan, and a shroud for forming an air guide passage extending fromthe radiator toward the rotary fan, the radiator-shroud structure beingcharacterized by comprising a surrounding portion which surrounds theouter circumference of the rotary fan at one end of the shroud, and aguide portion extending from a circumferential edge of the surroundingportion in a radially outward direction.

Since the guide portion extending outward in the radial direction of thefan is provided at the circumferential edge of the surrounding portionof the shroud, the centrifugally flowing air discharged from the rotaryfan flows along the guide portion. Therefore, the air flow turbulence atthe end of the surrounding portion can be mitigated. Thus, a sufficientamount of air passing through the radiator is secured, and the coolingcapacity of the radiator can be enhanced.

The width of the guide portion is desirably set to about 6% the diameterof the rotary fan. That is, when the rotary fan has a diameter of 500mm, the width of the guide portion is about 30 mm. Further, the guideportion is desired to assume an annular shape and extend over the entirecircumference. However, the guide portion may be partially removed so asto prevent interference with other parts such as a radiator hose.

EFFECTS OF THE INVENTION

By virtue of the radiator-shroud structure according to the presentinvention, the air flow turbulence at the end of the surrounding portionof the shroud can be mitigated, and the amount of air passing throughthe radiator is increased. Thus, the cooling capacity of the radiatorcan be enhanced. Moreover, since the rigidity of the surrounding portionincreases, the clearance between the fan and the surrounding portion canbe designed to be small so as to effectively prevent air leakage, andnoise radiated from the shroud can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a radiator-shroud structure according anembodiment of the present invention.

FIG. 2 is a perspective view of the radiator-shroud structure.

FIG. 3 shows results of flow simulation.

FIG. 4 is a graph showing the relation between length of a guide portionand air-amount change ratio.

FIG. 5 is an explanatory view of a cab-over-type vehicle.

FIG. 6 is a perspective view of a conventional radiator-shroudstructure.

FIG. 7 is a sectional view of the conventional radiator-shroudstructure.

FIG. 8 shows the results of simulation of turbulent flow for the case ofthe conventional radiator-shroud structure.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will next be described in detailwith reference to the drawings. FIG. 1 is a sectional view of aradiator-shroud structure according an embodiment of the presentinvention; FIG. 2 is a perspective view of the radiator-shroudstructure; FIG. 3 shows results of a simulation in which air flow issimulated for the case where the shroud has a guide portion; and FIG. 4is a graph showing the relation between length of the guide portion andair-amount change ratio.

As shown in FIG. 1, a radiator 13 is attached to a frame extending undera cab 3 of a cab-over-type vehicle 1. In FIG. 1, the left side of theradiator 13 corresponds to the front direction of the vehicle 1. In manycases, the radiator 13 is obliquely disposed as shown in the drawing inorder to increase surface efficiency.

Meanwhile, in the case of a truck, rotation is transmitted from a pulleyprovided on a crankshaft of an engine to a pulley provided on a rotaryshaft of a rotary fan 11. Therefore, the rotary fan 11 is attached to anengine section 5 present on the right side of the rotary fan 11 in FIG.1.

The rotary fan 11 can be of an axial flow type or a centrifugal flowtype. When the rotary fan 11 is of an axial flow type, an air flow leaksat the clearance between the end of the fan and the shroud, and theamount of air passing through the radiator 13 decreases. Therefore, inthe present embodiment, the rotary fan 11 is of a centrifugal flow type.The centrifugal-flow-type rotary fan 11 can be obtained by determiningthe shape of the rotary fan 11 in consideration of the coarseness of thegrid of the radiator 13.

When the centrifugal-flow-type rotary fan 11 is used, most of airflowing out of the radiator 13 and through the rotary fan 11 flows inthe centrifugal direction of the rotary fan 11. Therefore, the air canbe caused to flow to the rear of the engine while avoiding the enginesection 5.

A shroud 15 is provided in order to guide to the rotary fan 11 airhaving passed through the radiator 13.

The shroud 15 is formed of, for example, a metal or a resin, and isattached to the radiator 13. As shown in FIG. 2, at a portion where theshroud 15 is attached to the radiator 13, the shroud 15 assumes arectangular shape to match the shape of the radiator 13. The shroud 15narrows toward the rotary fan 11, and in the vicinity of the rotary fan11, the shroud 15 is formed into a cylindrical shape so as to surroundthe rotary fan 11. Further, in order to efficiently guide air to therotary fan 11, a tubular surrounding portion 17 is provided on theshroud 15. Further, in order to eliminate turbulence of thecentrifugally flowing air, a guide portion 19, which preferably has anannular shape, is provided at an end portion of the surrounding portion17. The surrounding portion 17 and the guide portion 19 of the shroud 15may be formed as a single member or as separate members, which are thenfixed together by use of rivets or the like.

Ideally, the clearance between the shroud 15 and the rotary fan 11 isset to zero, from the viewpoint of efficient guiding of air. However,since the shroud 15 is attached to the radiator 13 and the rotary fan 11is attached to the engine section 5, the shroud 15 is designed anddisposed in such a manner that a small space is provided between theshroud 15 and the rotary fan 11 in consideration of deformation andvibration during travel.

Since the guide portion 19 as shown in FIGS. 1 and 2 is provided on theshroud 15, air from the rotary fan 11 flows in the centrifugal directionalong the guide portion 19, whereby turbulence can be prevented.

FIG. 3 shows the results of simulation of turbulent flow for the casewhere the guide portion 19 is provided. As can be seen from FIG. 3, theturbulence is mitigated as compared with the case of FIG. 8.

FIG. 4 shows the relation between the length of the guide portion 19 andthe change ratio of amount of air passing through the radiator 13. Theamount of air starts to increase when the length of the guide portion 19is set to a or greater, and the increase in the amount of air saturateswhen the length becomes β or greater. Therefore, the length of the guideportion 19 is desired to be set to a value near β.

The results of this experiment show that a good result is attained whenthe length of the guide portion 19 is set to about 6% the diameter ofthe rotary fan 11. That is, in the case where the rotary fan 11 has adiameter of 500 mm, a good result is attained when the length of theguide portion 19 is set to about 30 mm.

The present invention is not limited to the above-described embodiment,and may be modified in various manners, and these modifications fallwithin the technical scope of the present invention. For example, in thepresent embodiment, the length of the guide portion 19 is set to about6% the diameter of the rotary fan 11. However, the length of the guideportion 19 is not limited thereto, and may change depending on the typeof the rotary fan 11, the shape of the shroud 15, and the like. Further,the shroud may be fixed to the engine or the frame, rather than theradiator. Moreover, the vehicle is not limited to the cab-over-typevehicle, and the present invention can be applied to a hood-typevehicle.

INDUSTRIAL APPLICABILITY

By virtue of the radiator-shroud structure according to the presentinvention, the turbulence of air flowing out of the rotary fan 11 in thecentrifugal direction can be mitigated, and the amount of air passingthrough the radiator 13 can be increased so as to enhance the coolingcapacity of the radiator 13.

1. A radiator-shroud structure comprising: a rotary fan which produces acentrifugal flow of air; a radiator provided in the vicinity of therotary fan; and a shroud for forming an air guide passage extending fromthe radiator toward the rotary fan, the radiator-shroud structure beingcharacterized by comprising: a surrounding portion which surrounds theouter circumference of the rotary fan at one end of the shroud; and aguide portion extending from a circumferential edge of the surroundingportion in a radially outward direction.
 2. A radiator-shroud structureaccording to claim 1, wherein the guide portion has a width about 6% thediameter of the rotary fan.